Tungsten Sulfido Alkylidene and Cationic Tungsten Sulfido Alkylidene N‑Heterocyclic Carbene Complexes

High-oxidation-state group 6 metal alkylidenes have been dominated by imido and oxo ligands. Here, the first neutral tungsten sulfido alkylidene and cationic tungsten sulfido alkylidene N-heterocyclic carbene (NHC) complexes are presented. A synthesis route that entails the reaction of the corresponding tungsten alkylidyne precursors with H2S in tetrahydrofuran is outlined. Schrock-type complexes bearing chlorides as well as pentafluorophenoxide ligands were synthesized, while variations in the NHC (1,3-dimesityl-1,3-dihydro-2H-imidazol-2-ylidene (IMes), 1,3-dimesityl-4,5-dichloro-1,3-dihydro-2H-imidazol-2-ylidene (IMesCl2), and 1,3-bis­(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene (IDipp)) as well as in the anionic ligand (chloride, pentafluorophenoxide, and 2,6-diphenylphenoxide) were carried out for the cationic tungsten sulfido alkylidene NHC complexes. All complexes were tested in benchmark olefin metathesis reactions in which the cationic tungsten sulfido alkylidene NHC complexes showed high productivities. Atomic charges were calculated for several cationic tungsten sulfido alkylidene NHC complexes and compared to those of the analogous tungsten oxo and imido complexes. These calculations revealed charge distribution between the NHC and the metal, yet lower charges at the metal and less polarization of the metal alkylidene bond compared to their tungsten oxo and imido analogs.

高氧化态第6族金属亚烷基配合物通常以亚胺基与氧配体为主。本文首次报道了中性硫化钨亚烷基配合物，以及阳离子型硫化钨亚烷基氮杂环卡宾（N-heterocyclic carbene, NHC）配合物。本文概述了一条合成路线：以相应的钨炔基前驱体与硫化氢在四氢呋喃中反应制备目标产物。我们合成了以氯离子与五氟苯氧基为配体的施罗克型配合物；针对阳离子型硫化钨亚烷基氮杂环卡宾配合物，还对氮杂环卡宾配体（包括1,3-二均三甲苯基-1,3-二氢-2H-咪唑-2-亚基(IMes)、1,3-二均三甲苯基-4,5-二氯-1,3-二氢-2H-咪唑-2-亚基(IMesCl₂)以及1,3-双(2,6-二异丙基苯基)-1,3-二氢-2H-咪唑-2-亚基(IDipp)）与阴离子配体（包括氯离子、五氟苯氧基以及2,6-二苯基苯氧基）的种类进行了调控。所有配合物均通过基准烯烃复分解反应进行了性能测试，结果显示阳离子型硫化钨亚烷基氮杂环卡宾配合物展现出优异的催化产率。我们对多款阳离子型硫化钨亚烷基氮杂环卡宾配合物开展了原子电荷计算，并将其与对应的钨氧及钨亚胺基配合物的电荷数据进行对比。计算结果表明，电荷在氮杂环卡宾与金属中心之间存在分布；但相较于对应的钨氧与钨亚胺基类似物，该类配合物的金属中心电荷更低，且金属亚烷基键的极化程度更弱。